Makeshift Piezo Earphones

A makeshift piezo earphone arrangement comprises a stethoscope and a piezo transducer.

The sound emanating from the transducer is captured by the bell of the stethoscope, held against its face.

Piezo Transducer
This arrangement was recently used to figure out how to interface a piezo earpiece with a crystal radio. The transducer, a 1¾" telephone ringer, was salvaged from the junk box.